World Trade Center 7: NIST vs. UAF, the Free-Fall Evidence, and the Questions That Still Deserve Answers

When a 47-story building collapses on September 11, 2001, without being struck by an airplane, the explanation deserves serious scrutiny. And when independent researchers challenge the official explanation with their own structural analysis, their work deserves the same scrutiny. The question isn't which side has the official stamp of approval. The question is which explanation best accounts for the evidence.

The third building

Most people know about the collapse of the World Trade Center's Twin Towers on September 11, 2001. Far fewer know much about World Trade Center Building 7, a 47-story steel-framed office building that collapsed at approximately 5:20 p.m. that afternoon.

Unlike the Twin Towers, WTC 7 was not struck by an aircraft. It sustained damage from debris when the North Tower collapsed, and fires burned in the building for hours. The National Institute of Standards and Technology (NIST) ultimately concluded that fires caused the building's collapse through a progressive sequence of structural failures.

That is the official explanation. But it is not the only technical explanation that has been published, and it has not gone unchallenged.

The University of Alaska Fairbanks (UAF) conducted an independent structural reevaluation under civil engineering professor J. Leroy Hulsey, with researchers Feng Xiao and Zhili Quan. Its final report, released in March 2020, reached a conclusion directly at odds with NIST's: fire did not cause WTC 7's collapse.

That disagreement deserves more than a quick dismissal.

What NIST says happened

NIST's final WTC 7 report, released in November 2008, proposed that fires heated floor beams and girders, causing thermal expansion and the failure of a critical support column, Column 79. According to NIST, that initial failure triggered a progressive collapse that spread through the building.

The theory is complex. It involves the behavior of floor framing, connections, girders, columns, and the way heat affected the building's structural system.

NIST's investigation was extensive. It included structural analysis, computer modeling, interviews, photographs, video, and information from building and emergency personnel. Its conclusions should be examined on their merits rather than dismissed simply because they came from a government agency.

But the same standard must apply in the other direction. NIST's status as the official investigative body does not make its conclusions immune from criticism.

The central question is whether its model adequately represented the building, its structural details, the actual conditions on September 11, and the collapse behavior recorded on video.

The free-fall issue: an important acknowledgment

One of the most important controversies concerns the speed at which WTC 7 descended.

In its initial public presentation in August 2008, NIST described the visible descent of the north face over approximately 18 stories as taking about 5.4 seconds. It compared this with an estimated 3.9 seconds for uninterrupted free fall, arguing that the overall descent took approximately 40 percent longer than free fall.

David Chandler challenged that analysis using video measurements.

NIST's final report subsequently described three stages of descent:

Stage 1: Approximately 1.75 seconds of acceleration below the rate of gravity.
Stage 2: Approximately 2.25 seconds of free-fall acceleration.
Stage 3: A period of deceleration as the descending structure encountered resistance below.

In other words, NIST acknowledged that the north face experienced approximately 2.25 seconds of free fall.

That is a significant admission. It means that during this interval, the structure below the descending portion was providing negligible resistance.

NIST maintained that this was consistent with its explanation: the exterior columns had buckled and lost their ability to support the upper structure. Chandler, however, continued to challenge the explanation for how the building transitioned into free fall, arguing that the observed transition was much more abrupt than NIST's progressive-collapse account would lead one to expect.

This distinction matters. Acknowledging free fall does not automatically establish why it happened. But neither should the free-fall interval be brushed aside as though it were insignificant.

The question is not whether gravity was involved. Obviously it was. The question is what happened to the building's structural support, and whether the proposed sequence adequately explains the observed motion.

For readers interested in the later analysis, David Chandler, Ted Walter, and Tony Szamboti published a 2023 paper revisiting the free-fall measurements and challenging NIST's explanation of the collapse sequence.

The University of Alaska Fairbanks study

The UAF study examined WTC 7 using structural modeling and several different approaches. Its researchers investigated the response of the building to fire loading, examined NIST's proposed collapse-initiation hypothesis, and modeled alternative structural failure scenarios.

The principal conclusion was direct: fire did not cause the collapse of WTC 7.

The researchers' secondary conclusion was equally consequential. They described the collapse as a global failure involving the near-simultaneous failure of every column in the building.

Let's be clear about what they meant.

The report describes a modeled scenario in which all core columns fail simultaneously over eight stories, followed 1.3 seconds later by the simultaneous failure of all exterior columns over eight stories. The researchers stated that this scenario produced almost exactly the behavior observed in collapse videos.

They also stated that, among the scenarios they simulated, this was the only one they identified that reproduced the observed behavior. They acknowledged that they could not completely rule out every possible alternative scenario.

The language is careful, as technical research language should be. But the implications are not difficult to understand.

The researchers were not describing a conventional sequence in which one local failure gradually spreads from column to column throughout the building. They were describing a rapid, coordinated structural failure across the building.

That is a profound difference from NIST's explanation.

The UAF report does not, by itself, establish what physical mechanism caused such a failure. It does not prove explosives were used. Those are separate questions requiring separate evidence. But its findings raise a serious question: if the observed collapse behavior is best reproduced by near-simultaneous failure of the columns, how should that result be reconciled with the official progressive-collapse explanation?

That question deserves a substantive answer, not a label.

The UAF project was funded by Architects & Engineers for 9/11 Truth, with a reported project budget of $316,153. That funding relationship should be disclosed. It is relevant when evaluating any research, just as the institutional setting and funding of other investigations are relevant.

But funding does not automatically invalidate a study. The proper questions concern its assumptions, methods, structural inputs, validation, limitations, and whether independent researchers can reproduce or challenge its results.

The final report and project materials are publicly available:

University of Alaska Fairbanks — A Structural Reevaluation of the Collapse of World Trade Center 7

Comparing the two explanations

There is an important difference between the kinds of claims being made.

NIST presents a fire-induced progressive-collapse scenario beginning with the failure of Column 79. UAF says it could not identify a progressive sequence of failures that would produce the observed total collapse in the scenarios it examined. Its modeled near-simultaneous failure scenario did reproduce the observed behavior.

Neither conclusion should be accepted merely because a researcher or institution says so.

A serious comparison needs to consider several issues:

1. Structural details and modeling assumptions

What structural components were included? Were the connections, stiffeners, plates, shear studs, and other relevant details represented accurately? How sensitive are the results to different assumptions?

2. The actual fire conditions

Were the fires sufficiently severe, and did they occur in the locations and for the duration required by the proposed failure sequence? How well do the models correspond to the available photographs, videos, eyewitness accounts, and building records?

3. The collapse sequence

Can the proposed mechanism explain the observed movement of the building, including the descent of the roofline, the penthouse behavior, and the free-fall interval?

4. Reproducibility and transparency

Can independent engineers examine the inputs, assumptions, calculations, and model results? Can they test competing scenarios and see whether the results hold up?

These are not unreasonable demands. They are basic questions for evaluating a complex engineering investigation.

NIST's modeling transparency problem

One issue that deserves particular attention is NIST's decision to withhold certain input and results files for its WTC 7 collapse models.

NIST says it withheld these files under the National Construction Safety Team Act because the detailed connection models could potentially be used to predict the collapse of similar buildings and help someone plan their destruction. A federal court upheld the decision.

That explanation should be accurately represented. It is not simply a case of NIST refusing to release information without offering a reason.

Nevertheless, there is a real scientific trade-off here. When a technical investigation relies on complex computer modeling, access to the model's underlying information can be important for independent verification. The public is being asked to trust a conclusion while certain detailed model files remain unavailable.

NIST's explanation may address its legal and public-safety rationale, but it does not make the scientific question of independent reproducibility disappear.

There are also specific modeling choices worth examining. For example, NIST acknowledges that its 16-story structural model did not include shear studs on the girders. It explains that the structural and erection drawings it relied upon did not show them on typical floors, while a modified Floor 10 drawing showed them in certain areas. NIST also says it performed a separate partial-floor analysis that explicitly modeled shear studs.

That is more nuanced than simply saying NIST ignored shear studs everywhere. But it remains a legitimate area for technical examination, particularly when competing researchers believe the omitted or differently represented structural details could affect the outcome.

NIST's own explanations should be read alongside the criticisms rather than replaced by them.

The debate over Hulsey's work

The UAF study did not emerge in a vacuum. It became the subject of public debate, including criticism from science writer and debunker Mick West.

West compared animations of NIST's model, the actual collapse, and Hulsey's simulations. He argued that NIST's model more accurately reproduced certain early collapse behavior, particularly the east penthouse, and questioned aspects of Hulsey's simulations.

Those are legitimate issues to examine. A model should be judged on how well it reproduces the observed event, not simply on whether its final conclusion agrees with one's preferred theory.

But the comparison also raises questions about what exactly is being compared. A model designed to investigate a particular failure scenario is not necessarily intended to reproduce every visible detail of the entire collapse. Conversely, a model that reproduces one part of the event more convincingly does not automatically establish that its proposed cause is correct.

I addressed this debate in my own 2019 response:

Debunking Mick West on Hulsey WTC 7 Report — NIST vs. Reality vs. Hulsey

I also assembled a broader comparison of the competing reports and the technical criticisms:

Are There More Problems with the UAF/Hulsey/AE911Truth WTC7 Draft Report or the NIST WTC 7 Report? You Decide...

The point is not that every criticism of Mick West is necessarily correct, or that every part of Hulsey's work is beyond criticism. The point is that the competing claims need to be examined in detail.

Independent engineering research deserves consideration

The UAF project is not the only work questioning the official explanation.

Robert Korol, Paul Heerema, and Ken Sivakumaran published a 2016 paper titled The Collapse of WTC 7: A Re-examination of the "Simple Analysis" Approach in the Challenge Journal of Structural Mechanics. The paper examined the official rationale and used basic engineering principles, including Newton's laws and energy considerations, to question whether the proposed collapse could be explained as described.

Another paper by Korol, Frank Greening, and Paul Heerema, Performance-Based Fire Protection of Office Buildings: A Case Study Based on the Collapse of WTC 7, appeared in the same journal in 2015.

These papers do not settle the debate. They do, however, demonstrate that technical criticism of the official explanation is not limited to internet commentary or people without engineering backgrounds.

The journal identifies its articles as double-blind peer reviewed. Peer review is not a guarantee that a paper is correct, but it is relevant information when evaluating whether research has undergone independent academic scrutiny.

My compilation of research and publication information is available here:

Peer-Reviewed 9/11 Truth

That collection covers a much wider range of 9/11 research, but it includes work relevant to WTC 7 and the broader debate over the engineering explanations.

It is also important to distinguish different kinds of publication. A peer-reviewed journal article, a conference paper, a technical report, a public presentation, and an advocacy organization's research project do not all go through the same process. They should not be casually treated as equivalent.

At the same time, the absence of conventional journal peer review does not automatically make an official investigative report correct. NIST's investigation was a government technical investigation, not a conventional journal article submitted for anonymous peer review. Its methods and conclusions should be evaluated directly.

What about former NIST personnel and other critics?

Another part of this debate concerns criticism from people who have worked in or around the government and engineering institutions involved in 9/11 investigations.

There have been public calls for independent review, criticisms from former government personnel, and disputes involving researchers and contractors with relevant technical experience.

Those claims should be assessed individually. A former employee's title does not automatically validate every conclusion they reach, just as an official employee's title does not automatically settle a scientific dispute.

But criticism from people familiar with the technical process should not be dismissed simply because it is inconvenient.

The same standard applies to everyone: What did they actually work on? What evidence do they provide? Are their claims firsthand? Can their technical arguments be checked?

That is how a serious investigation should proceed.

What does all of this establish — and what doesn't it?

There is a temptation in this debate to jump directly from an unusual collapse to a definitive explanation for how it was caused.

That is not necessary.

We can establish several important points without claiming more than the evidence supports:

WTC 7 was not struck by an airplane.
NIST concluded that fires initiated a progressive collapse.
NIST acknowledged a period of approximately 2.25 seconds of free-fall acceleration during the visible descent.
David Chandler and other researchers challenged NIST's interpretation of the transition into free fall.
The UAF team concluded that fire did not cause the collapse.
UAF's modeled near-simultaneous column-failure scenario reproduced the observed collapse behavior in a way its other simulated scenarios did not.
There are published engineering papers that challenge aspects of the official explanation.
NIST withheld certain detailed model files, citing public-safety concerns.
The competing explanations involve assumptions and modeling choices that deserve independent technical examination.

None of these points, by itself, proves controlled demolition. But neither does the existence of an official explanation mean the questions have been answered to everyone's satisfaction.

If a researcher proposes that a building's columns failed in a near-simultaneous sequence, the obvious next question is what could have caused that sequence. That question should be investigated rather than avoided.

There is a difference between saying a study has established a particular structural failure pattern and saying it has identified the physical mechanism responsible. Keeping those questions separate makes the discussion stronger, not weaker.

The bottom line: examine the evidence, not the labels

For years, the WTC 7 debate has often been reduced to a contest of labels: official investigators versus conspiracy theorists, professional engineers versus activists, science versus pseudoscience.

Those labels do not answer the engineering questions.

NIST's report deserves examination. Hulsey's report deserves examination. Chandler's video analysis deserves examination. The independent engineering papers deserve examination. Criticisms from Mick West and others deserve examination too.

And when a study challenges the accepted explanation, the response should be to engage with its methods and findings, not simply to point out who funded it or who supports it.

I have spent years examining 9/11 research, including the official investigations and the criticisms of those investigations. I don't believe people should be expected to accept a conclusion simply because it appears in an official report. Nor should they accept an alternative conclusion simply because it challenges the government.

The standard should be the evidence.

WTC 7 remains an important case study in how we investigate major events, how we handle conflicting scientific conclusions, and how much transparency the public should expect when government agencies present technical explanations for extraordinary events.

The question is not whether we are allowed to question the official explanation. The question is why we wouldn't.

Medical Disclaimer

Saturday, November 7, 2026